This document contains all the vSphere 5.5 maximums. Here are some of the figures for my quick reference:
| Hosts per vCenter Server (Appliance)(embedded vPostgres database) | 100 |
| VMs per vCenter Server (Appliance)(embedded vPostgres database) | 3000 |
| Hosts per vCenter Server (Appliance)(Oracle database) | 1000 |
| VMs per vCenter Server (Appliance)(Oracle database) | 10000 |
| Hosts per vCenter Server (Windows)(bundled SQL Server Express database) | 5 |
| VMs per vCenter Server (Windows)(bundled SQL Server Express database) | 50 |
| Hosts per vCenter Server (Windows)(external database) | 1000 |
| VMs per vCenter Server (Windows)(external database) | 10000 |
So the Windows install with inbuilt database is the lowest of the lot. You are better of going with the appliance (which has its own limitations of course).
Maximums of appliance and Windows server are the same as long as they use an external database. But appliance can only use Oracle as an external database while Windows server can use SQL too.